A wafer employed for various kinds of semiconductor devices can generally be obtained by cutting out a crystalline ingot such as Si or GaAs at specific intervals so as to be formed into a plate and mirror polishing its surface wherein a diamond blade saw or a wire saw for metal cutting is employed heretofore. Namely, an ingot is cut out with impact caused by pressing a diamond blade rotating at a high speed or a wire saw vibrating at a high speed thereon.
Besides, thus obtained wafer surface is processed in minute detail, for example, by a recessing process so that semiconductor devices such as a large scale integrated circuit (LSI) can be formed. As such a minute process, there are a method wherein a wafer surface is melted with a carbon dioxide gas laser, a YAG laser or the like and evaporated so as to be recessed, a method wherein resist is applied on a wafer surface and etching is conducted by a specific method after exposure so that a recess can be formed.
However, there is a problem in cost effectiveness in the method of cutting out a crystalline ingot because it is impossible to cut out only the part cut into by a diamond blade or a wire and also the neighborhood is deformed or destroyed so that an extra space in a sizeable thickness is wasted. More specifically, about 500 .mu.m thickness is wasted to cut out a piece of wafer, which means about 50% of an ingot may be wasted when cutting out a wafer of 500 .mu.m thickness. In addition, as such tools are repeatedly used for cutting out, the edge may be nicked and the sharpness may deteriorate, so that a diamond blade, a wire or the like requires time-consuming work of periodical replacement. Further, there is another problem that smear of cutting fluid charged into portions to be cut as purposes for cooling and lubrication, and debris caused in a cutting process may scatter and deteriorate the work environment. Still further, the cutting fluid including the debris is difficult to be recycled or disposed because a troublesome process, i.e., separation of the debris and the cutting fluid is indispensable.
In the meantime, in a method wherein a laser or the like is employed for minutely processing a wafer, there are problems that processing accuracy is not good because a wafer surface is melted so that melted liquid may swell or flow, and that a wafer component which is melted and evaporated may adhere to the other part of the wafer surface, be cooled and hardened, resulting in deterioration in surface smoothness. Meanwhile, in a method wherein etching is conducted after application of resist, for example, photoresist (photosensitive organic high polymer) 52 is applied on a surface of a wafer 51 of FIG. 9, as shown in FIG. 10, and a photo mask 53 wherein a predetermined circuit pattern (net portions Rs) is printed is attached thereon and exposed to light (FIG. 11). After being developed, unexposed parts (solved into developing solution) of the resist 52 are flowed away as shown in FIG. 12 so that a pattern forms on the surface of the wafer 51. Subsequently, a recess 54 can be formed (shown in FIG. 13) by plasma dry etching or the like using the resist 52 as a mask and the resist 52 is peeled off and cleaned, resulting in a wafer 51 (shown in FIG. 14) wherein a recess 54 as a circuit pattern is formed. This is a complicated process and means bad productivity. Furthermore, all the resist 52 applied on the whole surface of the wafer 51 is removed finally, which brings about high cost in materials and disposal or recycle of the liquid.
Accordingly, it is an object of the present invention to provide a superior method for processing a semiconductor material, for example, cutting of a crystalline ingot, minute processing on a wafer surface and the like, hygienically, easily and precisely, and an apparatus employed therein.
To accomplish the above object, the first gist of the present invention is a method for processing a semiconductor material comprising steps of supplying etching gas to a surface of the semiconductor material, while applying laser radiation or light quantum irradiation on a predetermined part thereof to be processed so as to be removed, exciting a gas component of the etching gas on the predetermined part, and chemically reacting a constituent of the semiconductor material and the excited gas component so as to be volatilized and removed.
Meanwhile, the second gist of the present invention is an apparatus employed for processing a semiconductor material comprising a closed chamber provided with a mounting part for mounting the semiconductor material and transporting means for moving the semiconductor material mounted on the mounting part, means for supplying etching gas into the chamber, means for withdrawing exhaust gas from the chamber, and means for exciting the etching gas by applying laser radiation or light quantum irradiation from the outside of the chamber on the mounted semicondutor material.